Integrated bicycle air pump

ABSTRACT

An air pump is integrated, in at least in part, in a seat tube of a frame of a bicycle. A flange is interposed between a seat post and the seat tube. The flange is secured to the seat post in a sliding abutment relationship with the seat tube. A seal located in a lower portion of the seat tube provides an air closure (i.e. an air seal). Hollow space between the flange and the seal in the seat tube form an air chamber for the air pump. A vent hole passes through the seat tube proximal to the air chamber. When the seat post is slid in a downward direction into the seat tube air is pressurized within the air chamber for expulsion through the vent hole.

TECHNICAL FIELD

The present invention relates generally to accessories for bicycles, and more particularly, to an air pump integrated as part of a bicycle.

BACKGROUND

Many bicyclists carry portable air pumps with them while riding to have them conveniently available to maintain proper air pressure in their tires, such as to refresh a slowly leaking tire. This also avoids the hassle of having to transport their bicycle to a repair shop or gas station to inflate their tires. Most modern portable air pumps are mountable on the bicycle frame to avoid the bicyclist having to carry the pump on their person while riding, which can be awkward and inconvenient.

However, there are drawbacks associated with mounting air pumps on the bicycle frame. For instance, pumps mounted to the bicycle frame may become dislodged and fall off, if jarred when riding over rough terrain. Additionally, pumps mounted to the bicycle frame, may become tempting items for thieves. Accordingly, when leaving their bike unattended when out riding, it is common for a bicyclist to remove their air pump from the frame and carry it with them.

Other drawbacks associated with portable air pumps are their inherent physical shortcomings. For example, a sufficient quantity of energy is required to inflate a tire, and for a conventional portable air pump the bicyclist usually compresses the air by pushing directly on a piston using a hand pumping motion. The compressive force required on the piston often becomes excessive at higher air pressures requiring substantial strength to move the pumping mechanism to push air into the tire. For example, it may take approximately 65 pounds of pressure to fully inflate a bicycle tire. Furthermore, it may require many strokes and substantial time to inflate a tire to its proper pressure due to the compact size of conventional portable air pumps, and their inability to produce sufficient quantities of air per stroke.

Another drawback of many portable air pumps involve the bicyclist having to bend down to the tire's level in an uncomfortable kneeling or bent over position and remain in this position while pumping the tire.

Still another drawback of many portable bicycle air pumps is that they tend to be expensive, as they are often constructed of lighter and inherently costlier materials to reduce weight and bulkiness.

SUMMARY

Briefly, this invention is directed to an air pump integrated, in at least in part, in a seat tube of a frame of a bicycle. A flange is interposed between a seat post and the seat tube. The flange is secured to the seat post in a sliding abutment relationship with the seat tube. A seal located in a lower portion of the seat tube provides an air closure (i.e. an air seal). Hollow space between the flange and the seal in the seat tube form an air chamber for the air pump. A vent hole passes through the seat tube proximal to the air chamber. When the seat post is slid in a downward direction into the seat tube air is pressurized within the air chamber for expulsion through the vent hole.

In another embodiment, a kit may be sold to bicycle repair shops and bicyclists that enables a user to retrofit a bicycle to include an integrated bicycle pump. The kit may include: a flange, a connection member, and a hose. The flange is secured to the seat post. A vent hole is drilled into the seat tube, and the connection member is mounted therein. The hose may be removeably secured to the connection member. Instructions describing how to retrofit a bicycle may accompany the kit or may be available from a web site.

This invention introduces the broad concept of creating an integrated bicycle air pump substantially out of standard bicycle parts in combination with only a few additional components. In particular, the combination of the seat post and the flange secured thereto form a piston of the integrated air pump. The bicycle seat serves as a handle for moving the piston up and down, and the seat tube form a housing for the piston. A vent hole in the seat tube proximal to the air chamber serves as an outlet for the integrated air pump, which enables a flexible hose to be connected for inflating tires, balls, rafts and other inflatable items.

This invention eliminates the need to purchase separate portable hand pumps for bicycles. Accordingly, most bicycles may be manufactured or retrofitted to include an air pump, simply by adding minimal extra parts per bicycle, such as a flange and a connection member. The additional extra parts add less than a few ounces of weight to the bicycle, and weigh less than most conventional portable tire pumps. Additionally, the parts are inexpensive, and usually do not require modification to the overall structure or design of the bicycle other than a small vent hole in the seat tube. It is noted that the seal used to plug the lower portion of the seat tube may or may not be needed depending on the construction of the seat tube. The seal may be constructed of inexpensive and lightweight material, such as rubber, metal, foam, or other suitable materials able to make the bottom of the seat tube generally air tight when air is compressed within the seat tube.

Another advantage of the integrated pump is the ability to pump bicycles tires while standing in a comfortable erect position. Once the hose is connected to a tire, the user of the pump moves the bicycle seat up and down, which admits air from the air chamber into the tire. The user of the innovative pump may simply push down on the bicycle seat using body weight rather than having to use shoulder and arm strength as is often the case with conventional portable pumps. Thus, yet another advantage of the innovative integrated pump is the ability to manually pump bicycle tires without having to use as much strength as a conventional portable bicycle air pump.

Another advantage of the innovative air pump is its ability to fully pump a tire to its proper pressure in less time than most conventional portable hand pumps, due to the larger size of the seat tube's air chamber when compared to many air chambers associated with conventional portable hand pumps. That is, the innovative pump described herein is able to produce larger quantities of air per stroke to pump into a tire. It is also easier to handle of the innovative integrated pump as it uses a much larger piston, i.e., the combination of seat, seat post and flange, when compared to many conventional portable bicycle air pumps.

Still a further advantage of the invention, is the convenience of always having a built-in air pump available as part of a bicycle, for inflating the tires of the bicycle or possibly other inflatable items. This invention eliminates many of the inconveniences associated with mounting a separately purchased air pump on a bicycle frame or other inconveniences such as searching for a repair station.

Further features and advantages of the present invention may become apparent after reading the Detailed Description section in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is presented with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. It is emphasized that the various features in the figures are not drawn to scale, and dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partial view of a bicycle.

FIG. 2 shows a grommet or o-ring (collectively a flange) fitting around the outer circumference of a seat post.

FIG. 3 shows a cross section view taken along line 3-3 of FIG. 2.

FIG. 4 shows a bicycle post sliding upward within a bicycle tube.

FIG. 5 shows a bicycle post sliding downward within a bicycle tube.

FIG. 6 shows a cross sectional view of a connection member proximal to an air chamber of the innovative air pump.

FIG. 7 shows a side view of a bicycle with an integrated pump therein.

FIG. 8 illustrates an aftermarket kit that may be used for converting a seat tube and a seat post of a frame of a bicycle (such as shown in FIGS. 1-7) into an integrated air pump.

DETAILED DESCRIPTION

Reference herein to “one embodiment”, “an embodiment”, or similar formulations, means that a particular feature, structure, operation, or characteristic described in connection with the embodiment, is included in at least one embodiment of the present invention. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. Furthermore, various particular features, structures, operations, or characteristics may be combined in any suitable manner in one or more embodiments.

Referring initially to FIG. 1 is a partial view of a bicycle generally shown as reference number 100. In particular, FIG. 1 shows a center portion of a bicycle frame 102 partly in cross section. Frame 102 includes a seat tube 104 (tube 104) with an opening 107 for receiving a seat post 106 (post 106) therein. Tube 104 is usually hollow in construction with an inner portion (or inner wall) 109 and an outer portion (or exterior wall) 111.

Typically, post 106, which is of a smaller concentric shape than tube 104, has an exterior surface 114 that fits within inner portion 109 of post 106. Post 106 has a large enough length to slide securely up and down within seat tube 104, in a concentric fashion. The ability to adjust the height of a bicycle seat 108 by sliding post 106 up or down is a fairly common feature of most bicycles, normally to accommodate different sized bicyclists. Typically, post 106 can slide up by lifting-upwards on seat 108, and can slide down by pushing downward on seat 108. Lubricants, such as oil or grease, allow post 106 to slide smoothly up and down (longitudinally), within tube 104.

A seat release mechanism, such as a threaded bolt or quick release lever 110, when loosened or placed in a release position, loosen a clamp (not shown) at opening 107. While the clamp is loosened, post 106 is able to slide freely in a longitudinal direction within tube 104 by pushing downward or pulling upward on seat 108. Conversely, when the clamp is tightened (e.g., seat release mechanism 110 placed locked into a non-release position) seat 108 is secured at a fixed height. For purposes of discussion herein, it assumed that release mechanism 110 is generally in a position to allow post 106 to slide freely up or down within tube 104.

Having introduced conventional features of most bicycles, it is now possible to describe embodiments of an innovative air pump integrated within bicycle 100 and using many standard parts of a bicycle.

Briefly, innovative air pump, referred to generally as reference number 116, includes one or more of the following components: a flange 118, a seal 120, a connection member 122, and a hose 124. As shall be explained these components in combination with the aforementioned parts of most conventional bicycles form innovative air pump 116. Each component and its interrelationship with bicycle 100 shall now be explained in greater detail.

Flange 118 is generally a flexible or semi-rigid material (such as rubber, plastic, neoprene, foam, or other suitable materials including composite materials) that may be configured in a variety of shapes and sizes able to be disposed between an inner wall 109 of tube 104 and an exterior portion 114 of post 106. For instance, in the illustrative embodiment of FIG. 1, flange 106 is a rubber grommet that fits between exterior portion 114 of post 106 and inner wall 109 of tube 104. Accordingly, when post 106 is inserted into tube 104, flange 118 remains coupled to post 106, and is interposed between post 106 and tube 104. That is, flange 118 is coupled to post 106 in a sliding abutment relationship with inner wall 109 of tube 104. Flange 118 typically presses against inner wall 108 in a resilient manner. In one embodiment, flange 118 has an outer portion 128 that extends beyond exterior portion 114 of post 106.

In alternative embodiments, flange 118 may be implemented as an o-ring, a disc, a flexible diaphragm, or any customized or off-the-shelf element suitable for use as a plunger of an air pump, i.e. a moveable seal for compressing air in the air chamber of an air hand pump.

Flange 118 may be secured to a bottom 125 of post 106 by any suitable manner. For instance, flange 118 may be mounted to bottom 125 by a bolt/washer (not shown), a backing plate (not shown), by glue, Velcro, adhesive, or other suitable fastening mechanisms. Flange 118 may also be an integral part of post 106.

Alternatively, flange 118 may be secured around an exterior portion 114 of post 106 in a concentric fashion, such as shown in FIG. 2. In the illustrative embodiment of FIG. 2, flange 118 is a rubber o-ring that fits in a groove 202 within exterior portion 114 of post 106. Flange 118 may also be glued or held in place by a pin (not shown), rod (not shown) or any other suitable fastening mechanism for securing flange 118 to exterior portion 114 of post 106. FIG. 3 shows a cross section view taken along line 3-3 of FIG. 2. In the illustrative embodiment of FIG. 3, flange 118 is disposed between inner wall 109 of tube 104 and exterior portion 114 of post 106.

In one implementation, flange 118 may flex and compress in shape. For example, when seat 108 is pulled upward causing post 106 to slide upward within tube 104, flange 118 flexes downward as its edges 402 slide against inner wall 109 of tube 104 (see FIG. 4). As shall be explained, this flexing of flange 118 permits ambient air to flow past edges of flange 118 in a downward direction into an air chamber 132 (to be explained), filling a vacuum.

In contrast, when seat 108 is pushed downward causing post 106 to slide downward within tube 104, flange 118 compresses in shape, causing edges 402 to thicken as edges 402 slide against inner wall 109 (see FIG. 5). As shall be explained, compression of flange 118 creates an air dam preventing air from flowing past flange 118 as air is compressed within air chamber 132. Therefore, flange 118 acts as a piston (or air dam) and pushes air out of an air chamber 132 (see FIG. 1 to be explained) while seat 108 is pushed downward.

Referring back to FIG. 1, seal 120 is a plug located in a lower portion 130 of tube 104 and provides an air closure blocking air from flowing past seal 120. In other words, seal 120 blocks air from entering or exiting gaps or openings (not shown) of lower portion 130 of tube 104.

Seal 120 may be of any material suitable for serving as an air closure inside tube 104. For example, seal 120 may be foam, plastic, rubber, epoxy, adhesive, metal, paper, sponge, cardboard, a composite material, or a combination of the aforementioned. Although seal 120 is illustrated as being single thin piece of material, it may be of various dimensions, and may not be even or uniform in shape, such as in the form of an a sealant such as epoxy or glue used for sealing gap(s) (not shown) in lower portion 130. Seal 120 may also be an integral part of frame 102. When implemented as a fixed structure, seal 120 may be secured in place by various means, depending on the type of material selected for seal 120. For example, if in the form of a liquid applied drying sealant, such as glue, seal 120 will stick to inner portions of frame 102. If of a different material such as plastic, rubber or material, seal 120 may be held in place by finishing to the surface of inner wall 109 or by other means, as those skilled in the art would readily appreciate.

Hollow space in the interior of tube 104, between flange 118 and seal 120 forms an air chamber 132. Accordingly, when post 106 is slid downward into tube 104, flange 118 moves toward seal 120 and acts as a piston. Flange 118 compresses air within air chamber 132. Pressure build-up in chamber 132 causes air therein to exit air chamber 132 via an air vent 121 located within connection member 122. Air vent 121 provides an air pathway for air to pass from inside chamber 132 to the exterior of tube 104 via connection member 122. That is, air pressure within air chamber 132 increases when post 106 is slid in a downward direction into tube 104 thereby causing flange 118 to slide with post 106 against inner wall 109 of tube 104 and push air out of vent hole (also referred to as air vent 121).

On the other hand, a reverse stroke of pump 116 occurs, when flange 118 is moved upward by pulling seat 108 in an upward direction. This action creates a vacuum in air chamber 132, which causes ambient air to enter air chamber 132 by flowing past flexed edges 402 (see also FIG. 4) of flange 118. That is, ambient air enters air chamber 132 when post 106 is slid in an upward direction thereby causing flange 118 to slide with post 106 against inner wall 109 of tube 104. A vacuum is simultaneously created by the action of flange 118 moving upward creating a greater volume void within tube 104, which causes ambient air to rush-in chamber 132 to fill the lower pressurized chamber 132. Thus, the ambient air flows past edges 402 (FIG. 4) of flange 118 between flange 118 and inner wall 109, and enters air chamber 132. At this point, a down stroke pump 116 can occur as explained above by pushing down on seat 108. The process of down strokes and up strokes may repeat several times until a desired pressure is reached in the vessel being inflated, such as a bicycle tire.

In one embodiment, connection member 122 is generally a closed body providing a pathway for air to exit air chamber 132 into hose 124, such as when post 106 is slid downward pumping compressed air into chamber 132. FIG. 6 shows a cross sectional view of connection member 122 according to one exemplary embodiment.

Referring to FIG. 6, connection member 122 includes walls 602 that pass through inner and outer portions 109, 111 of tube 104. Walls 602 are either integral to inner and outer portions 109, 111 of tube 104, are connected thereto by an air tight sealant such as epoxy and/or solder, or are connected by other suitable means as will be appreciated by those skilled in this field and having the benefit of the present disclosure. Vent hole 121 may be drilled through tube 104, or may be punch pressed item and integrated therein. In one embodiment, vent hole 121 has a diameter of 0.25 inches.

Connection member 122 includes a check valve 604. In one implementation, check valve 604 includes a ball 606 configured to cover and seal a hole 608. In turn, ball 606 prevents air from flowing from hose 124 into air chamber 132 when post 106 and flange 118 are moved upward. As mentioned earlier when flange 118 is moved upward it creates a vacuum in air chamber 132 (see also FIG. 4), and forces ambient air to enter air chamber 132 around flexed edges 402 (see also FIG. 4) of flange 118. Again, ball 606 prevents air from entering air chamber 132 when this vacuum is created.

On the other hand, when post 106 is slid downward (see also FIG. 5) into tube 104, flange 118 slides toward seal 120 pressurizing air within chamber 132 for expulsion through the vent hole forcing air to compress in air chamber 132 and exit air vent 121. Exiting air flows up through hole 608 past ball 606, causing ball 606 to float. The air then flows around the levitating ball 606 and exits hole 612 and into hose 124. A wire 610 prevents ball 606 from being pushed-up into hole 612 and block hole 612 when air exits connection member 122. Alternatively, a bar (not shown) or other restraint structure may also be used to contain ball 606. Ball 606 may be made of various materials such as rubber, Styrofoam, plastic, or other suitable materials. Additionally, it will be appreciated by those skilled in this field and having the benefit of the present disclosure, that check valve 604 may be implemented using a one-way diaphragm valve instead of a ball, or by other suitable means.

Connection member 122 also provides a means for attaching hose 124. In one embodiment, hose 124 is releasably engaged/disengaged to connection member 122. Hose 124 may be engaged/disengaged by a connection interface 150, such as threaded screw interface, bayonet twist-on/twist-off mechanisms, snap-on/snap-off mechanisms, or by other suitable connection mechanisms. Alternatively, hose 124 may be an integrated part of connection member 122.

Referring back to FIG. 1, hose 124 is generally made of flexible material(s) such as rubber or other materials commonly used with manual air pumps. Hose 124 is preferably long enough to reach the front and rear tires of a bicycle, but may be of different lengths depending on the size of a bicycle and its tires. At the distal end of hose 124 is an inflation valve 152 for engaging the valve (not shown) of a bicycle tire. Alternatively, inflation valve 152 may include interchangeable parts configured to mate with other inflation interface mechanisms, such as a pin for interfacing with an intake valve of a ball (e.g., beach ball, football, soccer ball, etc.). An air gauge (not shown) may be included as part of pump 116.

It will be appreciated by those skilled in this field and having the benefit of the present disclosure, that flange 118 may be implemented using a non-flexible material. Accordingly, flange 118 may provide a permanent seal when post 106 is slid upward or downward. In such an exemplary implementation, a check valve (not shown) may be implemented in seal 120 (or other location within frame 102) that allows air to flow into chamber 132 when post 106 is slid upward, and seals itself when post 106 is slid downward. Accordingly, check valve 604 is optional and may be implemented in another portion of pump 116.

FIG. 7 shows a side view of bicycle 100 with an integrated pump 116 therein. In particular, FIG. 7 shows that hose 124 may be held onto frame 102 by attachment elements 702 (see FIG. 7), such as clips, Velcro straps, or other suitable restraint pieces.

FIG. 8 illustrates an aftermarket kit 802 for converting a seat tube and a seat post of a frame of a bicycle (such as shown in FIGS. 1-7) into an integrated air pump such as the foregoing pump 116. Kit 802 may be sold as a package directly or indirectly to bicyclists and bicycle retail/repair shops.

In one implementation, kit 802 includes a grommet 804 securable to the seat post (such as 106) of a bicycle. Grommet 804 (also referred to as a flange) is adapted to be interposed between the seat post and an inner wall (e.g., 109 of FIG. 1) of a seat tube. Grommet 804 when installed on the bottom of seat post such as shown in FIGS. 1, 2 and 3 is also configured to be in sliding engagement with the inner wall of the seat tube.

Kit 802 may also include a coupling mechanism (such as connection member 122 shown in FIGS. 1 and 6) configured to provide an air conduit between a vent hole (e.g., 121 of FIGS. 1 and 6) and a hose 124 (FIGS. 1 and 6), the vent hole 121 (FIGS. 1 and 6) passing through a wall of the seat tube 104 into a hollow portion of the seat tube forming an air chamber 132 (FIGS. 1 and 6) therein.

Kit 802 may also include a hose, such as hose 124 (FIGS. 1 and 6), which also may include a coupling mechanism such as connection mechanism 150. Kit 802 may also include a plug, such as seal 120 (FIG. 1) for providing an air seal at a location within the seat tube below the vent hole.

It should also be appreciated that kit 802 may include instructions describing how to install the grommet, the coupling mechanism, and the hose to construct an integrated air pump 116 (FIG. 1) partially within bicycle 100. The instructions may be in paper form or available electronically, such as from a web site.

The embodiments described herein are to be considered in all respects only as exemplary and not restrictive. The scope of the invention is, therefore, indicated by the subjoined Claims rather by the foregoing description. All changes which come within the meaning and range of equivalency of the Claims are to be embraced within their scope. 

1. An air pump integrated, in at least in part, in a seat tube of a frame of a bicycle, comprising: a flange interposed between the seat post and the seat tube the flange secured to the seat post in a sliding abutment relationship with the seat tube; a seal located in a lower portion of the seat tube providing an air closure, wherein space between the flange and the seal in the seat tube form an air chamber; and a vent hole providing an air passage out of the air chamber, whereby as the seat post is slid downward into the seat tube the flange slides toward the seal pressurizing air within the air chamber for expulsion through the vent hole.
 2. The air pump as recited in claim 1, wherein the combination of the seat post and the flange secured thereto form a piston of the air pump, wherein the seat serves as a handle for moving the piston up and down, and wherein the seat tube forms a housing for the piston.
 3. The air pump as recited in claim 1, whereby as the seat post is slid downward into the seat tube, the flange compresses against the seat tube forming an air dam.
 4. The air pump as recited in claim 1, whereby as the seat post is slid upward in a direction away from the seal, the flange flexes permitting ambient air to enter the air chamber, the ambient air flowing between the flange and the seat tube.
 5. The air pump as recited in claim 1, further comprising a hose connected to the vent hole, the hose having an inflation valve at a distal end of the hose furthest from the vent hole.
 6. The air pump as recited in claim 1, whereby ambient air enters the air chamber as the seat post is slid upward in the seat tube creating a vacuum within the air chamber which causes ambient air to flow between the flange and the seat tube, and fill the air chamber.
 7. The air pump as recited in claim 1, further comprising a hose connected to the vent hole having an inflation valve at a distal end of the hose furthest from the vent hole, the inflation valve adapted to releasably engage a tire valve.
 8. The air pump as recited in claim 1, further comprising a hose releasably connected to the vent hole.
 9. The air pump as recited in claim 1, further comprising a check valve connected to the vent hole, the check valve permitting air to exit the air chamber as the seat post is slid downward into the seat tube, and the check valve blocking air from flowing into the air chamber through the vent hole as the seat post is slid upward in the seat tube.
 10. The air pump as recited in claim 1, further comprising a check valve connected to the vent hole, the check valve permits air to exit the air chamber and blocks air from flowing into the air chamber through the vent hole.
 11. An air pump integrated within a seat tube of a frame of a bicycle, comprising: a flange interposed between a seat post and an inner wall of the seat tube, the flange secured to the seat post in sliding engagement with the inner wall of the seat tube thereby forming an air chamber within the seat tube below the flange; and a vent hole passing through a wall of the seat tube providing an airway between the air chamber and the exterior of the frame of the bicycle; whereby air pressure within the air chamber increases when the seat post is slid in a downward direction into the seat tube thereby causing the flange to slide with the seat post against the inner wall of the seat tube and push air out of the vent hole, and whereby ambient air enters the air chamber when the seat post is slid in an upward direction thereby causing the flange to slide within the seat post against the inner wall of the seat tube creating a vacuum which causes ambient air to pass between the flange and the inner wall, and enter the air chamber.
 12. The air pump as recited in claim 11, further comprising a hose connected to the vent hole.
 13. The air pump as recited in claim 11, further comprising a hose releasably connected to the vent hole via a connection member.
 14. The air pump as recited in claim 11, further comprising a seal located in a lower portion of the seat tube below the vent hole.
 15. The air pump as recited in claim 11, further comprising a seal located in a lower portion of the seat tube below the vent hole, the seal blocking air from escaping the lower portion the seat tube and forming a portion of the air chamber between the flange and the inner wall of the seat tube.
 16. The air pump as recited in claim 11, further comprising a check valve connected to the vent hole.
 17. The air pump as recited in claim 11, further comprising a check valve connected to the vent hole, the check valve permits air to exit the air chamber and blocks air from flowing into the air chamber through the vent hole.
 18. A kit for converting a seat tube and seat post of a frame of a bicycle into an air pump, the air pump kit comprising: a grommet securable to the seat post of a bicycle, the grommet adapted to be interposed between a seat post and an inner wall of the seat tube and in sliding engagement with the inner wall of the seat tube; and a coupling mechanism configured to provide an air conduit between a vent hole and a hose, the vent hole passing through a wall of the seat tube into a hollow portion of the seat tube forming an air chamber therein.
 19. The kit as recited in claim 18, further comprising a hose configured to attach to the coupling mechanism.
 20. The kit as recited in claim 18, further comprising a plug residing within the seat tube, the plug providing an air seal at a location within the seat tube below the vent hole. 